Single shaft shifting mechanisms for selecting and engaging the selectable ratios of a multiple speed vehicular mechanical transmission are known in the prior art as may be seen by reference to U.S. Pat. No. 4,621,537 and German Patent No. 1011736, the disclosures of which are hereby incorporated by reference. Such mechanisms are, in certain situations, improvements relative to the multiple parallel shift rail type devices as disclosed in U.S. Pat. Nos. 4,445,393; 4,275,612; 4,584,895 and 4,722,237, the disclosures of which are hereby incorporated by reference, as they require fewer parts, utilize a single moving shaft making the use of improved bearings and finishes more economically feasible, require less space, allow easier control of an auxiliary transmission and/or allow easier more economical sensing of transmission neutral and transmission in-gear conditions.
While the prior art single shaft shifting mechanisms were useful in certain situations, they were not totally satisfactory as the hub or block portions of the various shift forks required multiple axially extending slots cut radially through the hub from the inner diameter to the outer diameter surfaces thereof which could weaken the hubs and which were somewhat difficult and expensive to produce.
Further, the prior art single shaft shifting mechanisms utilized rather complicated cross-shaft mechanisms which included the various detent and stop mechanisms and thus did not allow for easy conversion of the transmission for both direct and remote shifting configurations.
U.S. Pat. No. 4,920,815 to Reynolds, assigned to the assignee of the present invention, addresses these shortcomings in the prior art. Reynolds discloses a single shaft shifting mechanism having two shift keys for contact with hubs and movement of shift forks. While Reynolds is a perfectly acceptable solution to these problems, it would be advantageous to reduce the costs and part complexity required in that design.